Early Monday morning, citing “serious health issues” in her family, Liz Cheney gave up her bid for the Republican U.S. Senate nomination in Wyoming.

"My children and their futures were the motivation for our campaign and they will always be my overriding priority," Cheney said in a statement, implying that one of her children is ailing. She did not disclose specifics.

It would be wrong to accuse Cheney of fabricating an excuse to drop out of a race she is losing. Cheneys, love 'em or loathe 'em, are not exactly quitters.

Still, she must have been feeling a little green around the gills about her closely watched but increasingly doomed campaign against the well-liked, three-term Republican incumbent, Mike Enzi. The polls, which showed her getting thumped, had to have been pretty sickening.

She may also have become nauseated by the idea that she put politics above family when she sold out her sister on national television to rebut charges that she was not sufficiently against gay marriage. This unnecessary and unpleasant family drama surely did nothing to endear Cheney to voters in her native state.

As Cheney learned the hard way, you cannot thread the needle on gay marriage anymore.

In 2009, when she worked for the State Department, Liz Cheney told MSNBC she opposed a constitutional amendment banning gay marriage and supported extending federal benefits to same-sex couples. Gay marriage, she said, should be decided by the states.

That gave a conservative Super PAC fodder for an attack ad depicting her as soft on gay marriage and “wrong for Wyoming.” Cheney might have used the opportunity to stand up for her sister, Mary, who had married her longtime partner, Heather Poe, in 2012. Instead, she accused her opponents of playing dirty with a “scurrilous” attack.

And then she really sold her sister out.

“I do believe in the traditional definition of marriage,” she told Fox News’ Chris Wallace. “Listen, I love Mary very much, I love her family very much, this is just an issue on which we disagree.”

Trivializing gay marriage as “just an issue” is like saying separate water fountains and racially segregated schools are “just an issue” on which some folks disagreed. Marriage equality is at the very heart of gay civil rights. If you can’t be married, you can’t be equal.

The family betrayal was compounded when their parents, former Vice President Dick Cheney and his wife, Lynne, put another knife in Mary Cheney’s back.

“Liz has always believed in the traditional definition of marriage,” the Cheneys said in a statement. “She has also always treated her sister and her sister's family with love and respect, exactly as she should have done. ... Liz's many kindnesses shouldn't be used to distort her position."

Was it simply a "kindness" when, according to Poe, Liz "didn't hesitate to tell us how happy she was for us" when the couple married in 2012?

You cannot be for gay marriage in private and against it in public.

Too bad the Cheneys were not kind enough, or loving enough, to add a sentence supporting their younger daughter. All they had to do was reiterate Dick Cheney’s support for gay marriage, articulated in 2009. They might have said: “We embrace our daughter's wife, and their family."

Instead, like their elder daughter, they put politics first.

Liz Cheney is not all that different from many Republicans who fail to grasp the connection between public policy and the well-being of families (unemployment benefits, food stamps, health insurance, etc.).

But if she wants to be part of “a new generation of Republican leadership” as she has said, that implies coming to terms with the reality of the social landscape. Gay marriage is out of the bag and it's not going back in.

Cheney needs to examine her conscience and figure out why she thinks it’s OK to denigrate her sister's family in a way she would never tolerate the denigration of her own.